CODEWITHSUNDEEP
python
xyz
xyz

Reputation: 403

What does the .N mean in this block of Python code?

I am working through Learn Python the Hard Way and am browsing through some code on Git Hub before moving on. I am just curious what the .N does on the line with "tm.N = 1000" and how it relates to the end of the code.

import matplotlib.pyplot as plt

import random
import pandas.util.testing as tm
tm.N = 1000
df = tm.makeTimeDataFrame()
import string
foo = list(string.letters[:5]) * 200
df['indic'] = list(string.letters[:5]) * 200
random.shuffle(foo)
df['indic2'] = foo
df.boxplot(by=['indic', 'indic2'], fontsize=8, rot=90)

plt.show()

Upvotes: 0

Views: 3261

Answers (7)

Vinod Kumar
Vinod Kumar

Reputation: 1622

.N provides the number of elements in array type. For example, if you use a colormap, plt.get_cmap('Pastel1').N will return 9 because it consists of 9 colors whereas plt.get_cmap('nipy_spectral').N will return 256

Upvotes: 1

xbello
xbello

Reputation: 7443

N is a global in the testing.py module, that is used all around the module to test arrays and other things. Its default value is 30. E.g.

np.arange(N * K).reshape((N, K))
Series(randn(N), index=index)

In the code you're posting it have poor usage, because makeTimeDataFrame can be feed with a nper parameter that end up being substituted by N if nper is not provided. This is the correct usage, that would not confuse you:

df = tm.makeTimeDataFrame(nper=1000)

Upvotes: 2

jakebrinkmann
jakebrinkmann

Reputation: 805

It makes a timeseries of length 1000. 

>>> df.head()
Out[7]: 
                   A         B         C         D
2000-01-03 -0.734093 -0.843961 -0.879394  0.415565
2000-01-04  0.028562 -1.098165  1.292156  0.512677
2000-01-05  1.135995 -0.864060  1.297646 -0.166932
2000-01-06 -0.738651  0.426662  0.505882 -0.124671
2000-01-07 -1.242401  0.225207  0.053541 -0.234740
>>> len(df)
Out[8]: 1000

Upvotes: 1

Kristian Damian
Kristian Damian

Reputation: 1356

In pandas in the module pandas.util.testing the N property means TimeSeries See this reference in the section:

We could alternatively have used the unit testing function to create a TimeSeries of length 20:


>>>> pandas.util.testing.N = 20
>>>> ts = pandas.util.testing.makeTimeSeries()

Upvotes: 1

Celeo
Celeo

Reputation: 5682

You can get information about pandas.util.testing.N from the docstring and the type() function:

>>> tm.N.__doc__
'int(x[, base]) -> integer\n\nConvert a string or number to an integer, if possible.  A floating point\nargument will be truncated towards zero (this does not include a string\nrepresentation of a floating point number!)  When converting a string, use\nthe optional base.  It is an error to supply a base when converting a\nnon-string.  If base is zero, the proper base is guessed based on the\nstring content.  If the argument is outside the integer range a\nlong object will be returned instead.'
>>> print(tm.N.__doc__)
int(x[, base]) -> integer

Convert a string or number to an integer, if possible.  A floating point
argument will be truncated towards zero (this does not include a string
representation of a floating point number!)  When converting a string, use
the optional base.  It is an error to supply a base when converting a
non-string.  If base is zero, the proper base is guessed based on the
string content.  If the argument is outside the integer range a
long object will be returned instead.
>>> type(tm.N)
<type 'int'>

Upvotes: 1

ThreeLLMsInATrenchcoat
ThreeLLMsInATrenchcoat

Reputation: 519

Source: https://github.com/pydata/pandas/blob/master/pandas/util/testing.py

N is a variable in the pandas.util.testing library (imported as tm). It's used in a few of the functions defined in that library, including the makeTimeSeries function called in the getTimeSeriesData which is in turn called in the makeTimeDataFrame function that you call with df = tm.makeTimeDataFrame()

Upvotes: 1

jwodder
jwodder

Reputation: 57490

The previous line, import pandas.util.testing as tm, imports the module pandas.util.testing and, for convenience, gives it the name tm. Thus, tm afterwards refers to this module, and so tm.N refers to the object named "N" (whatever that is) in the module.

Upvotes: 2

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